Excess glucose is converted to glycogen, which is stored in the liver and muscles and serves as a source of energy between meals, during sleep and during exercise. In the liver, excess glucose is converted into In the human liver, excess glucose is converted into

There is a lot of useful information about the benefits and harms of glucose, the consequences of its overdose. We will do our part too. First you need to find out what this product is.

Glucose is a carbohydrate - a monosaccharide. It is also called dextrose or grape sugar. It is, first of all, a natural nutrient that gives people energy, helps overcome stressful situations and enhances metabolism.

Meaning

Today everyone has already heard conversations about the benefits of this product and its excellent properties. It is a colorless, odorless substance, sweetish in taste and soluble in water. How is glucose useful? It is presented as a wonderful alternative to sugar, and it is, because now everything natural is highly valued. Its highest content is in grape juice (hence, by the way, the second name of the substance), as well as in some fruits.

However, one should not think that glucose cannot harm the body. Excess daily norm may be harmful to the body. Serious illnesses may occur. Elevated levels of grape juice are called hyperglycemia.

Dosage and daily norm

The glucose norm for humans is 3.4-6.2 mmol/l. If there is a shortage or, conversely, an increased content in the blood, painful deviations occur. In the liver, excess glucose is converted into glycogen.

If the body does not produce sufficient amounts necessary for normal operation pancreas, then the monosaccharide does not enter the cells and accumulates in the blood. This serious disease in medicine is called diabetes mellitus.

With poor nutrition, low-carbohydrate or simply unbalanced diets, a lack of substance in the body may occur. This condition can cause confusion, slow brain function, and anemia.

Benefit

Quite a lot has already been said about the benefits and harms of glucose.

Everyone knows that nutrients, obtained from food eaten, are absorbed by people as proteins, fats and carbohydrates. The latter components, in turn, are broken down into glucose and fructose. Grape juice transports beneficial substances into the body's cells and fills them with energy.

Glucose affects the functioning of the cardiovascular, nervous, respiratory and muscular systems.

It is also no secret that more than half of a person’s energy comes from eating foods high in this substance, as well as glycogen, which is synthesized in the liver.

It has enormous benefits on the central nervous system, because the brain exclusively uses this monosaccharide to maintain its work. And with a lack or absence of glucose, the nervous system and blood cells begin to waste glycogen reserves.

Also, the beneficial effects of this monosaccharide are manifested:

1. In improving mood and protecting during stressful situations.
2. Maintaining the functioning of the cardiovascular system at a sufficient level.
3. In muscle recovery. Scientists and doctors have long proven the effectiveness of taking glucose after exercise, along with proteins. The sooner after physical activity, glucose enters the blood, the faster muscle will begin to recover.
4. Energy restoration.
5. Improving mental activity, learning ability and mental abilities.

Beneficial features

Grape juice is an extremely important component for the vitality of the body. Due to its low calorie content, it is absorbed into the blood very quickly.

The influence of glucose affects work of cardio-vascular system, liver, muscles. As a result of its use, the heart can beat and muscles contract. Mental abilities and learning abilities are enhanced, and work nervous system normalizes.

Harm

As already mentioned, a lack of glucose is called hypoglycemia and can lead to absolutely different symptoms. One thing is certain - the harm from this disorder is quite great.

First of all, the lack of grape juice affects the functioning of the central nervous system. After all, she is extremely sensitive. Brain function deteriorates, a person’s visual memory is impaired, and it becomes very difficult to solve any problems.

There may be several circumstances that contribute to hypoglycemia. For example, this disease can accompany diabetics throughout their lives. Other reasons are strict diets with unbalanced amounts of proteins, fats and carbohydrates, irregular nutrition, and pancreatic tumors.

The symptoms are:

• chills:
• poor coordination of movements;
• tremor of hands and feet;
• low mental activity;
• confusion;
• bad memory.

But, in turn, an overdose of glucose, or, more precisely, high level consumption of this monosaccharide may contribute to:

1. Increased body weight, gain of extra pounds, premature obesity.
2. The appearance of blood clots.
3. Atherosclerosis.
4. Elevated cholesterol levels.

Contraindications

There are several categories of people for whom it is extremely undesirable, if not prohibited, to consume glucose in food. These are, for example, well-known diabetics, whose body reacts even to eating candy or an orange with a sharp jump in carbohydrates in the blood.

Patients with diabetes should reduce the consumption of products containing this component to a minimum. Only under such conditions can patients keep their cardiovascular system in order.

Even for people of retirement age and the elderly, glucose intake should also be minimal. Because when its level is elevated, their metabolism is disrupted.

Obese patients should avoid sweets containing glucose, due to the fact that its excess in the body is converted into triglyceride and contributes to coronary disease heart, the occurrence of blood clots.

Purpose

There are situations when a doctor prescribes additional consumption of a monosaccharide to a patient. Such circumstances include:

• during the rehabilitation period after surgery;
• during pregnancy, if the fetus is underweight;
• in case of poisoning with drugs or various chemicals;
• for long-term infectious diseases.

Output

This monosaccharide is also available in different forms, for convenient use. For example:

1. In tablet form - this form is intended to improve brain function and quick learning;
2. In the form of a solution for installing droppers - this form is also prescribed to animals. In the case of treating dogs with vomiting and diarrhea, use a glucose solution to avoid dehydration;
3. In the form of intravenous injections - in this case, glucose acts as a diuretic medication.

Video: glucose and glycogen, what is it?

Application

In addition to medicinal use, glucose plays a major role in the fermentation process. Therefore, it is used in the production of fermented milk products (kefir, fermented baked milk, etc.), as well as grape wines, kvass, and bakery products.

It is also used in medical practice for infections, chronic fatigue syndrome and weak immunity.

We can summarize: glucose is an extremely important source of nutrition and energy for the body.

When taken in acceptable doses, the monosaccharide enhances brain function, improves the overall well-being of the body and improves mood. But if there is a shortage or excess of it in the blood, there is a risk of blood clots, cancer, obesity and high blood pressure.

2533. Endocrine glands secrete hormones in

B) organ cells

2534. Choose an example of aromorphosis

A) the formation of nectaries in flowers

B) the formation of differences in the structure of flowers in plants

C) the appearance of the root system in ancient ferns

D) the formation of various leaves in plants

2535. Are they true? the following judgments about the forms of natural selection?

1. The emergence of resistance to pesticides in insect pests of agricultural plants is an example of a stabilizing form of natural selection.

2. Driving selection contributes to an increase in the number of individuals of a species with an average value of the trait

A) only 1 is correct

B) only 2 is correct

C) both statements are correct

D) both judgments are wrong

2536. The absence of mitochondria, the Golgi complex, and the nucleus in the cell indicates its belonging to

2537. Lysosome is

A) a system of interconnected tubules and cavities

B) an organelle delimited from the cytoplasm by one membrane

B) two centrioles located in the dense cytoplasm

D) two interconnected subunits

2538. What kind of reproduction ensures the genetic diversity of plants?

2539. An organism whose homologous chromosomes contain genes for dark and light hair color is

2540. In conditions tropical Africa White cabbage does not form heads. What form of variability is manifested in this case?

In the liver, excess glucose is converted into

Excess glucose in the liver is converted into

In the Schools section, to the question What happens in the liver with excess glucose? asked by the author Denis Shumakov the best answer is that in the liver glycogen is formed from glucose under the influence of the hormone insulin

monitor the alt and ast enzymes!

I don’t know what happens to the liver from glucose, but I know for sure that when you eat sweets, inflammation begins, the liver enlarges, and all this is driven off by glucose and ascorbic acid

Great Encyclopedia of Oil and Gas

Excess - glucose

In the hepatic vein and vessels great circle blood circulation during normal conditions The glucose content is kept at a constant level and fluctuates within very small limits - from 85 to HO mg per 100 ml of blood. The constancy of the sugar content in the hepatic vein is explained by the fact that excess glucose is retained by the liver. With a small intake, glucose completely passes into the hepatic vein, and with a large intake, excess glucose is converted into glycogen under the influence of liver enzymes. The process of formation of glycogen from glucose and its deposition as a reserve nutrient material in the liver and partly in the muscles is activated by the pancreatic hormone insulin.

The entire complex of metabolic changes caused by insulin deficiency can be considered as evidence that in diabetes the body strives to convert all the nutrients at its disposal into blood glucose. Tissues are in dire need of glucose, and the liver intensively synthesizes it, but this only leads to most of glucose goes into the urine. According to this view of metabolic disorders in diabetes, the patient's tissues are unable to absorb glucose from the blood when it is normal level, constituting mm; they require a much higher concentration of glucose for efficient absorption. However, when the blood glucose concentration increases above 10 mM, i.e. above the kidney threshold, excess glucose is excreted in the urine, causing the body to lose large amounts of glucose.

In plants, the glucose molecule is polymerized into chains consisting of thousands of monomer units, resulting in cellulose, and if the polymerization occurs in a slightly different way, the result is starch. Closely related to glucose, N-acetylglucosamine, as a result of polymerization, forms chitin, the substance that makes up the cornea of ​​insects. Another substance of similar composition, N-acetylmuranoic acid, copolymerizes into a different sequence of chains from which the walls of bacterial cells are built. Glucose decomposes in several stages, releasing energy that is required by a living organism. Excess glucose is carried by the bloodstream to the liver and converted into animal starch - glycogen, which is converted back into glucose when needed. Glucose, cellulose, starch and glycogen are carbohydrates.

In Fig. Table 8.2 shows the results of such extracellular digestion. Amylases and proteinases respectively break down starch into glucose and proteins into amino acids. The thin and well-branched mycelium of Mysog and Rhizopus provides a large absorption surface. Glucose is used during respiration to provide the fungus with the energy necessary for metabolic processes. In addition, glucose and amino acids are used for the growth and restoration of fungal tissues. The cytoplasm stores excess glucose, converted into glycogen and fat, and excess amino acids in the form of protein granules.

Starch constitutes, by weight, the main component of human food (bread, potatoes, cereals, vegetables) - the main energy resource of his body. Already in the mouth, under the influence of saliva containing the hydrolytic enzyme amylase, the hydrolysis of starch begins. In the acidic environment of the stomach, hydrolysis is completed by splitting into glucose, which from the intestine enters the blood and is carried by the blood current to each cell, undergoing a series of transformations there (p. Glucose concentration is regulated by the action of hormones. When the glucose content in the blood increases, its excess due to the specific action of the secreted pancreas, the hormone insulin (protein, see book II) is deposited in the liver and partially in the muscles in the form of animal starch - glycogen. The liver can contain up to 20 weight. If the activity of the pancreas is impaired and it does not produce insulin, diabetes mellitus occurs. , characterized by increased levels of glucose in the blood.The body is then forced to dump excess glucose in the urine.

I will allow myself to say a few words here about the work that I have just begun, but which, perhaps, will lead to a solution to the question that interests us. Some considerations led me to the conclusion that the dehydration of glucose in plants can only occur with the help of a special enzyme acting in the opposite direction than amylase. The existence of these two enzymes with diametrically opposed functions is not unexpected, since we now know that in a living organism there exist one or more oxidative enzymes - oxidases - and one hydrogenating enzyme. If a hydrating enzyme exists, then it is quite possible that a dehydrating enzyme also exists. The following characteristic fact makes this assumption very plausible. It is known that amylase does not act on starch in the presence of a concentrated glucose solution. Let us assume that the plant contains, along with amylase, a dehydrating enzyme. During the period when the process of carbon assimilation occurs at full intensity in the leaves and glucose is formed, the latter is converted into starch by our hypothetical enzyme. In the presence of excess glucose, amylase has no effect on starch deposited in the leaves. But as soon as assimilation stops, the amount of glucose decreases, and amylase becomes active again: it converts starch into soluble sugary substances necessary for the life of the plant.

Liver

Bulanov Yu.B.

The name "liver" comes from the word "oven", because. the liver has the most high temperature from all organs of the living body. What is this connected with? Most likely due to the fact that the highest amount of energy production occurs in the liver per unit mass. Up to 20% of the mass of the entire liver cell is occupied by mitochondria, the “power stations of the cell,” which continuously produce ATP, which is distributed throughout the body.

The purpose of the portal vein is not to supply the liver with oxygen and rid it of carbon dioxide, but to pass through the liver all the nutrients (and non-nutrients) that have been absorbed throughout the gastrointestinal tract. First, they pass through the portal vein through the liver, and then in the liver, having undergone certain changes, they are absorbed into the general bloodstream. The portal vein accounts for 80% of the blood received by the liver. The portal vein blood is mixed. It contains both arterial and venous blood flowing from the gastrointestinal tract. Thus, in the liver there are 2 capillary systems: the usual one, between the arteries and veins, and the capillary network of the portal vein, which is sometimes called the “miraculous network”. The normal and capillary miraculous networks are interconnected.

Sympathetic innervation

The liver is innervated by the solar plexus and branches vagus nerve(parasympathetic impulses).

Carbohydrate metabolism

Glucose and other monosaccharides entering the liver are converted into glycogen. Glycogen is stored in the liver as a “sugar reserve”. In addition to monosaccharides, lactic acid, products of the breakdown of proteins (amino acids), and fats (triglycerides and fatty acids) are also converted into glycogen. All these substances begin to turn into glycogen if there are not enough carbohydrates in food.

Protein metabolism

The role of the liver in protein metabolism is the breakdown and “rearrangement” of amino acids, the formation of chemically neutral urea from ammonia, which is toxic to the body, as well as the synthesis of protein molecules. Amino acids, which are absorbed in the intestine and formed during the breakdown of tissue protein, constitute the body’s “reservoir of amino acids,” which can serve as both a source of energy and a building material for protein synthesis. Isotopic methods It was found that in the human body, protein is broken down and re-synthesized. Approximately half of this protein is transformed in the liver. The intensity of protein transformations in the liver can be judged by the fact that liver proteins are renewed in about 7 (!) days. In other organs, this process occurs in at least 17 days. The liver contains the so-called “reserve protein”, which is used for the body’s needs if there is not enough protein in food. During a two-day fast, the liver loses approximately 20% of its protein, while the total protein loss of all other organs is only about 4%.

Fat metabolism

The liver can store much more fat than glycogen. The so-called “structural lipid” - structural lipids of the liver - phospholipids and cholesterol make up 10-16% of the dry matter of the liver. This number is fairly constant. In addition to structural lipids, the liver contains inclusions of neutral fat, similar in composition to subcutaneous fat. The content of neutral fat in the liver is subject to significant fluctuations. In general, we can say that the liver has a certain fat reserve, which, if there is a deficiency of neutral fat in the body, can be spent on energy needs. In case of energy deficiency, fatty acids can be well oxidized in the liver with the formation of energy stored in the form of ATP. In principle, fatty acids can be oxidized in any other internal organs, but the percentage will be as follows: 60% liver and 40% all other organs.

Cholesterol metabolism

Cholesterol molecules form the structural framework of all cell membranes without exception. Cell division is simply impossible without sufficient cholesterol. Bile acids are formed from cholesterol, i.e. essentially bile itself. All steroid hormones are formed from cholesterol: glucocorticoids, mineralocorticoids, and all sex hormones.

Vitamins

All fat-soluble vitamins (A, D, E, K, etc.) are absorbed into the intestinal walls only in the presence of bile acids secreted by the liver. Some vitamins (A, B1, P, E, K, PP, etc.) are deposited by the liver. Many of them are involved in chemical reactions occurring in the liver (B1, B2, B5, B12, C, K, etc.). Some vitamins are activated in the liver, undergoing phosphorication there (B1, B2, B6, choline, etc.). Without phosphorus residues, these vitamins are completely inactive and often the normal vitamin balance in the body depends more on the normal state of the liver than on the sufficient intake of one or another vitamin in the body.

Hormone exchange

Role of the liver on metabolism steroid hormones is not limited to the fact that it synthesizes cholesterol - the basis from which all steroid hormones are then formed. In the liver, all steroid hormones are inactivated, although they are not formed in the liver.

Microelements

The metabolism of almost all microelements directly depends on the functioning of the liver. The liver, for example, influences the absorption of iron from the intestine; it deposits iron and ensures the constancy of its concentration in the blood. The liver is a depot of copper and zinc. It takes part in the exchange of manganese, molybdenum, cobalt and other microelements.

Bile formation

Bile, produced by the liver, as we have already said, takes an active part in the digestion of fats. However, the matter is not limited to just their emulsification. Bile activates the fat-splitting enzyme liposis of pancreatic and intestinal juice. Bile also accelerates the absorption in the intestines of fatty acids, carotene, vitamins P, E, K, cholesterol, amino acids, and calcium salts. Bile stimulates intestinal motility.

They still use it now. Fiber in vegetables and fruits, but even more so, pectin substances, have the ability to absorb bile acids and remove them from the body. The largest amount of pectin substances is found in berries and fruits, from which jelly can be made without the use of gelatin. First of all, these are red currants, then, according to their gelling ability, they are followed by black currants, gooseberries, and apples. It is noteworthy that baked apples contain several times more pectin than fresh ones. Fresh apples contain protopectins, which turn into pectins when apples are baked. Baked apples are an indispensable attribute of all diets when you need to remove a large amount of bile from the body (atherosclerosis, liver disease, some poisoning, etc.).

Excretory (excretory) function

The excretory function of the liver is very closely related to bile formation, since substances excreted by the liver are excreted through bile and, if only for this reason, they automatically become an integral part of bile. These substances include the hormones already described above. thyroid gland, steroid compounds, cholesterol, copper and other trace elements, vitamins, porphyrin compounds (pigments), etc.

Substances excreted almost exclusively with bile are divided into two groups:

• · Substances bound to proteins in the blood plasma (for example, hormones).
• · Substances insoluble in water (cholesterol, steroid compounds).

One of the features of the excretory function of bile is that it is capable of introducing substances from the body that cannot be removed from the body in any other way. There are few free compounds in the blood. Most of the same hormones are tightly bound to transport proteins in the blood and, being firmly bound to the proteins, cannot overcome the kidney filter. Such substances are excreted from the body along with bile. Another large group of substances that cannot be excreted in urine are substances that are insoluble in water.

Neutralizing function

The liver plays a protective role not only by neutralizing and removing toxic compounds, but even by microbes that get into it, which it destroys. Special liver cells (Kupffer cells), like amoebas, capture foreign bacteria and digest them.

Blood clotting

The liver synthesizes substances necessary for blood clotting, components of the prothrombin complex (factors II, VII, IX, X), the synthesis of which requires vitamin K. The liver also produces fibranogen (a protein necessary for blood clotting), factors V, XI, XII , XIII. Strange as it may seem at first glance, the synthesis of elements of the anticoagulant system occurs in the liver - heparin (a substance that prevents blood clotting), antithrombin (a substance that prevents the formation of blood clots), and antiplasmin. In embryos (fetuses), the liver also serves as a hematopoietic organ where red blood cells are formed. With the birth of a person, these functions are taken over by the bone marrow.

Redistribution of blood in the body

The liver, in addition to all its other functions, performs quite well as a blood depot in the body. In this regard, it can affect the blood circulation of the entire body. All intrahepatic arteries and veins have sphincters, which can change blood flow in the liver over a very wide range. On average, blood flow in the liver is 23 ml/kx/min. Normally, almost 75 small vessels of the liver are excluded from the general circulation by sphincters. With an increase in total blood pressure, liver vessels dilate and hepatic blood flow increases several times. On the contrary, a drop in blood pressure leads to vasoconstriction in the liver and hepatic blood flow is reduced.

Age-related changes

The functionality of the human liver is highest in early childhood and decrease very slowly with age.

Liver

Why does a person need a liver?

The liver is our largest organ, its weight ranges from 3 to 5% of body weight. The bulk of the organ consists of hepatocyte cells. This name is often found when it comes to liver functions and diseases, so let’s remember it. Hepatocytes are specially adapted for the synthesis, transformation and storage of many various substances, which come from the blood - and in most cases return there. All our blood flows through the liver; it fills numerous hepatic vessels and special cavities, and around them a continuous thin layer of hepatocytes is located. This structure facilitates the exchange of substances between liver cells and blood.

There is a lot of blood in the liver, but not all of it is “flowing.” Quite a significant amount of it is in reserve. With a large loss of blood, the liver vessels contract and push their reserves into the general bloodstream, saving the person from shock.

Bile secretion is one of the most important digestive functions of the liver. From the liver cells, bile enters the bile capillaries, which unite into a duct that flows into the duodenum. Bile, together with digestive enzymes, breaks down fat into its components and facilitates its absorption in the intestines.

The liver synthesizes and breaks down fats

Liver cells synthesize some fatty acids and their derivatives needed by the body. True, among these compounds there are also those that many consider harmful - these are low-density lipoproteins (LDL) and cholesterol, the excess of which forms atherosclerotic plaques in blood vessels. But don’t rush to scold the liver: we cannot do without these substances. Cholesterol is an essential component of the membranes of erythrocytes (red blood cells), and it is LDL that delivers it to the site of red blood cell formation. If there is too much cholesterol, red blood cells lose their elasticity and have difficulty squeezing through thin capillaries. People think that they have problems with blood circulation, but their liver is not in order. A healthy liver prevents the formation of atherosclerotic plaques; its cells remove excess LDL, cholesterol and other fats from the blood and destroy them.

The liver synthesizes blood plasma proteins.

Almost half of the protein that our body synthesizes per day is formed in the liver. The most important among them are blood plasma proteins, primarily albumin. It accounts for 50% of all proteins created by the liver. There must be a certain concentration of proteins in the blood plasma, and it is albumin that maintains it. In addition, it binds and transports many substances: hormones, fatty acids, microelements. In addition to albumin, hepatocytes synthesize blood clotting proteins that prevent the formation of blood clots, as well as many others. When proteins age, their breakdown occurs in the liver.

Urea is formed in the liver

Proteins in our intestines are broken down into amino acids. Some of them are used in the body, while the rest must be removed because the body cannot store them. The breakdown of unnecessary amino acids occurs in the liver, which produces toxic ammonia. But the liver does not allow the body to be poisoned and immediately converts ammonia into soluble urea, which is then excreted in the urine.

The liver turns unnecessary amino acids into necessary ones

It happens that a person’s diet lacks some amino acids. The liver synthesizes some of them using fragments of other amino acids. However, the liver cannot make some amino acids; they are called essential and a person receives them only from food.

The liver converts glucose into glycogen and glycogen into glucose

There must be a constant concentration of glucose (in other words, sugar) in the blood serum. It serves as the main source of energy for brain cells, muscle cells and red blood cells. The most reliable way to ensure a constant supply of glucose to your cells is to store it after meals and then use it as needed. This most important task is assigned to the liver. Glucose is soluble in water and is inconvenient to store. Therefore, the liver catches excess glucose molecules from the blood and converts glycogen into an insoluble polysaccharide, which is deposited in the form of granules in liver cells, and, if necessary, is converted back into glucose and enters the blood. The glycogen reserve in the liver lasts for hours.

The liver stores vitamins and microelements

The liver stores fat-soluble vitamins A, D, E and K, as well as water-soluble vitamins C, B12, niacin and folic acid. This organ also stores minerals, necessary for the body in very small quantities, such as copper, zinc, cobalt and molybdenum.

The liver destroys old red blood cells

In the human fetus, red blood cells (red blood cells that carry oxygen) are produced in the liver. Gradually, this function is taken over by bone marrow cells, and the liver begins to play the exact opposite role - it does not create red blood cells, but destroys them. Red blood cells live for about 120 days and then age and must be removed from the body. The liver has special cells that trap and destroy old red blood cells. This releases hemoglobin, which the body does not need outside of red blood cells. Hepatocytes disassemble hemoglobin into “spare parts”: amino acids, iron and green pigment. The liver stores iron until it is needed to form new red blood cells in the bone marrow, and turns the green pigment into yellow - bilirubin. Bilirubin enters the intestines along with bile, which turns yellow. If the liver is diseased, bilirubin accumulates in the blood and stains the skin - this is jaundice.

The liver regulates the levels of certain hormones and active substances

In this organ, excess hormones are converted into an inactive form or destroyed. The list is quite long, so here we will only mention insulin and glucagon, which are involved in the conversion of glucose into glycogen, and the sex hormones testosterone and estrogens. In chronic liver diseases, the metabolism of testosterone and estrogen is disrupted, and the patient develops spider veins, underarm and pubic hair falls out, and in men, the testicles atrophy. The liver removes excess active substances such as adrenaline and bradykinin. The first of them increases the heart rate, reduces the outflow of blood to the internal organs, directing it to the skeletal muscles, stimulates the breakdown of glycogen and an increase in blood glucose levels, and the second regulates the water and salt balance of the body, contractions of smooth muscles and capillary permeability, and also performs some other functions. It would be bad for us with an excess of bradykinin and adrenaline.

The liver destroys germs

The liver has special macrophage cells that are located along blood vessels and catch bacteria from there. Once caught by microorganisms, these cells are swallowed and destroyed.

As we have already understood, the liver is a resolute opponent of everything unnecessary in the body, and of course it will not tolerate poisons and carcinogenic substances in it. Neutralization of poisons occurs in hepatocytes. After complex biochemical transformations, toxins are converted into harmless, water-soluble substances that leave our body in urine or bile. Unfortunately, not all substances can be neutralized. For example, when paracetamol breaks down, it produces a potent substance that can permanently damage the liver. If the liver is unhealthy, or the patient has taken too much paracetomol, the consequences can be dire, including the death of liver cells.

Based on materials from zdorovie.info

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What happens in the liver with excess glucose? Scheme of glycogenesis and glycogenolysis

Glucose is the main energy material for the functioning of the human body. It enters the body with food in the form of carbohydrates. Over the course of many millennia, man has undergone a lot of evolutionary changes.

One of the important acquired skills was the body’s ability to store energy materials for future use in case of famine and synthesize them from other compounds.

Excess carbohydrates accumulate in the body with the participation of the liver and complex biochemical reactions. All processes of accumulation, synthesis and use of glucose are regulated by hormones.

What role does the liver play in storing carbohydrates in the body?

There are the following ways for the liver to use glucose:

1. Glycolysis. A complex multi-stage mechanism of glucose oxidation without the participation of oxygen, which results in the formation of universal energy sources: ATP and NADP - compounds that provide energy for all biochemical and metabolic processes in the body;
2. Storage in the form of glycogen with the participation of the hormone insulin. Glycogen is an inactive form of glucose that can accumulate and be stored in the body;
3. Lipogenesis. If more glucose is supplied than is necessary even for the formation of glycogen, lipid synthesis begins.

The role of the liver in carbohydrate metabolism is enormous; thanks to it, the body constantly has a supply of carbohydrates that are vital for the body.

What happens to carbohydrates in the body?

The main role of the liver is the regulation of carbohydrate metabolism and glucose with the subsequent deposition of glycogen in human hepatocytes. A special feature is the transformation of sugar under the influence of highly specialized enzymes and hormones into its special form; this process occurs exclusively in the liver ( necessary condition consumption by cells). These transformations are accelerated by the enzymes hexo- and glucokinase when the sugar level decreases.

During the digestion process (and carbohydrates begin to break down immediately after food enters the oral cavity) the glucose content in the blood increases, resulting in an acceleration of reactions aimed at deposition of excess. This prevents the occurrence of hyperglycemia during meals.

Sugar from the blood, through a series of biochemical reactions in the liver, is converted into its inactive compound - glycogen and accumulates in hepatocytes and muscles. When energy starvation occurs, with the help of hormones, the body is able to release glycogen from the depot and synthesize glucose from it - this is the main way to obtain energy.

Glycogen synthesis scheme

Excess glucose in the liver is used in the production of glycogen under the influence of the pancreatic hormone insulin. Glycogen (animal starch) is a polysaccharide, the structural feature of which is a tree-like structure. It is stored by hepatocytes in the form of granules. The glycogen content in the human liver can increase up to 8% of the cell mass after eating a carbohydrate meal. Breakdown is generally needed to maintain glucose levels during digestion. With prolonged fasting, glycogen content drops to almost zero and is synthesized again during digestion.

Biochemistry of glycogenolysis

If the body's need for glucose increases, glycogen begins to break down. The conversion mechanism occurs, as a rule, between meals, and accelerates when muscle loads. Fasting (no food intake for at least 24 hours) leads to almost complete breakdown of glycogen in the liver. But with regular nutrition, its reserves are completely restored. Such accumulation of sugar can exist for a very long time, before the need for breakdown arises.

Biochemistry of gluconeogenesis (pathway to glucose production)

Gluconeogenesis is the process of synthesis of glucose from non-carbohydrate compounds. Its main task is to maintain a stable level of carbohydrates in the blood during a lack of glycogen or heavy physical work. Gluconeogenesis ensures the production of sugar up to 100 grams per day. In a state of carbohydrate starvation, the body is able to synthesize energy from alternative compounds.

To use the glycogenolysis pathway when necessary to obtain energy, the following substances are needed:

1. Lactate (lactic acid) is synthesized during the breakdown of glucose. After physical activity, it returns to the liver, where it is again converted into carbohydrates. Due to this, lactic acid is constantly involved in the formation of glucose;
2. Glycerol is the result of lipid breakdown;
3. Amino acids are synthesized during the breakdown of muscle proteins and begin to participate in the formation of glucose when glycogen reserves are depleted.

The main amount of glucose is produced in the liver (more than 70 grams per day). The main task of gluconeogenesis is to supply sugar to the brain.

Carbohydrates enter the body not only in the form of glucose - it can also be mannose contained in citrus fruits. Mannose, as a result of a cascade of biochemical processes, is converted into a compound similar to glucose. In this state, it enters into glycolysis reactions.

Scheme of the regulatory pathway for glycogenesis and glycogenolysis

The pathway of glycogen synthesis and breakdown is regulated by the following hormones:

• Insulin is a pancreatic hormone of protein nature. It lowers blood sugar. In general, a feature of the hormone insulin is its effect on glycogen metabolism, as opposed to glucagon. Insulin regulates the further pathway of glucose conversion. Under its influence, carbohydrates are transported into the cells of the body, and from their excess, glycogen is formed;
• Glucagon, the hunger hormone, is produced by the pancreas. It has a protein nature. In contrast to insulin, it accelerates the breakdown of glycogen and helps stabilize blood glucose levels;
• Adrenaline is a hormone of stress and fear. Its production and secretion occur in the adrenal glands. Stimulates the release of excess sugar from the liver into the blood to supply tissues with “nutrition” in a stressful situation. Just like glucagon, unlike insulin, accelerates the catabolism of glycogen in the liver.

A change in the amount of carbohydrates in the blood activates the production of the hormones insulin and glucagon, changing their concentration, which switches the breakdown and formation of glycogen in the liver.

One of the important tasks of the liver is to regulate the lipid synthesis pathway. Lipid metabolism in the liver includes the production of various fats (cholesterol, triacylglycerides, phospholipids, etc.). These lipids enter the blood, their presence provides energy to the body's tissues.

The liver is directly involved in maintaining energy balance in the body. Her diseases can lead to disruption of important biochemical processes, as a result of which all organs and systems will suffer. It is necessary to carefully monitor your health and, if necessary, do not delay visiting a doctor.

Attention! Information about drugs and folk remedies treatment is presented for informational purposes only. Under no circumstances should you use the medicine or give it to your loved ones without medical advice! Self-medication and uncontrolled use of drugs are dangerous for the development of complications and side effects! At the first signs of liver disease, you should consult a doctor.

©18 Editorial staff of the portal “My Liver”.

The use of site materials is permitted only with prior approval from the editor.

1) glycogen

2) hormones

3) adrenaline

4) enzymes

145. Harmful substances formed during the digestion process are neutralized in

1) large intestine

2) small intestine

3) pancreas

146. The process of food passing through the digestive tract is ensured

1) mucous membranes of the digestive tract

2) secretions of the digestive glands

3) peristalsis of the esophagus, stomach, intestines

4) activity of digestive juices

147. Absorption of nutrients in the human digestive system occurs most intensively in

1) stomach cavity

2) large intestine

3) small intestine

4) pancreas

148. When there is a lack of bile in the human body, absorption is impaired.

3) carbohydrates

4) nucleic acids

149. Where does the preparatory stage of energy metabolism take place in humans?

1) in the cytoplasm of cells

2) in the digestive tract

3) in mitochondria

4) on the endoplasmic reticulum

150. In which part of the human digestive canal is the bulk of water absorbed?

1) oral cavity

2) esophagus

3) stomach

4) colon

151. Sneezing is a reflex sharp exhalation through the nose that occurs when receptors located on the mucous membrane are irritated

1) root of tongue and epiglottis

2) cartilages of the larynx

3) trachea and bronchioles

4) nasal cavity

152. What nutrients enter the human blood during absorption through the villi of the small intestine?

1) amino acids

3) polysaccharides

4) nucleic acids

153. Urine in humans is formed in

1) urethra

2) bladder

3) ureters

4) nephrons

154. The lack of vitamins in human food leads to metabolic disorders, since vitamins are involved in the formation

1) carbohydrates

2) nucleic acids

3) enzymes

4) mineral salts

Vitamins in the human and animal body

1) regulate the supply of oxygen

2) influence growth, development, metabolism

3) cause the formation of antibodies

4) increase the rate of formation and breakdown of oxyhemoglobin

Rye bread is a source of vitamin

Vitamin is synthesized in human skin under the influence of ultraviolet rays

1) destroys poisons secreted by microbes

2) destroys poisons secreted by viruses

3) protects enzymes responsible for antibody synthesis from oxidation

4) is a component of antibodies

What vitamin is part of the visual pigment contained in the light-sensitive cells of the retina?

What vitamin should be included in the diet of a person with scurvy?

What role do vitamins play in the human body?

1) are a source of energy

2) perform a plastic function

3) serve as components of enzymes

4) affect the speed of blood movement

Vitamin A deficiency in humans leads to disease

1) night blindness

2) diabetes mellitus

4) rickets

IN fish oil a lot of vitamin:

Lack of vitamin A in the human body leads to disease

1) night blindness

2) diabetes mellitus

4) rickets

165. Lack of vitamin C in the human body leads to disease

1) night blindness

2) diabetes mellitus

4) rickets

Lack of vitamin D in the human body leads to disease

1) night blindness

2) diabetes mellitus

4) rickets

167. Consumption of foods or special medications containing vitamin D,

1) increases muscle mass

2) prevents rickets

3) improves vision

4) increases hemoglobin content

168. B vitamins are synthesized by symbiont bacteria in

2) stomach

3) colon

4) small intestine

Human phagocytes are capable

2) produce hemoglobin

3) participate in blood clotting

4) produce antibodies

The first barrier to microbes in the human body is created

1) hair and glands

2) skin and mucous membranes

3) phagocytes and lymphocytes

4) red blood cells and platelets

What happens in the human body after a protective vaccination?

1) enzymes are produced

2) blood coagulates, a blood clot forms

3) antibodies are formed

4) the constancy of the internal environment is disrupted

172. What virus disrupts the work immune system person:

1) polio

173. The body’s immunity to the effects of the pathogen is ensured by:

1) metabolism

2) immunity

3) enzymes

4) hormones

AIDS can lead to:

1) to blood incoagulability

2) to the complete destruction of the body’s immune system

3) to a sharp increase in the content of platelets in the blood

4) to a decrease in hemoglobin in the blood and the development of anemia

In emergency cases, the patient is administered a therapeutic serum, which contains:

1) weakened pathogens

2) toxic substances secreted by microorganisms

3) ready-made antibodies against the pathogen of this disease

4) dead pathogens

176. Preventive vaccinations protect a person from:

1) any diseases

2) HIV infection and AIDS

3) chronic diseases

4) most infectious diseases

177. During a preventive vaccination, the following is introduced into the body:

1) killed or weakened microorganisms

2) ready-made antibodies

3) leukocytes

4) antibiotics

The human body is protected from foreign bodies and microorganisms by

1) leukocytes, or white blood cells

2) erythrocytes, or red blood cells

3) platelets, or blood platelets

4) the liquid part of the blood is plasma

The introduction of serum containing antibodies against pathogens of a certain disease into the blood leads to the formation of immunity

1) active artificial

2) passive artificial

3) natural congenital

4) natural acquired

Leukocytes are involved in

1) blood clotting

2) oxygen transfer

3) transfer of final metabolic products

4) destruction of foreign bodies and substances

The body’s defense against infection is carried out not only by phagocyte cells, but also

1) red blood cells

2) platelets

3) antibodies

4) Rh factor

Vaccination of the population is

1) treatment of infectious diseases with antibiotics

2) strengthening the immune system with stimulants

3) introduction of weakened pathogens to a healthy person

4) administration of antibodies to the causative agent of the disease to a sick person

Mother's milk protects infants from infectious diseases, as it contains:

1) enzymes

2) hormones

3) antibodies

4) calcium salts

Passive artificial immunity occurs in a person if the following is injected into his blood:

2) ready-made antibodies

3) phagocytes and lymphocytes

4) red blood cells and platelets

The vaccine contains

1) only poisons secreted by pathogens

2) weakened or killed pathogens or their poisons

3) ready-made antibodies

4) unattenuated pathogens in small quantities

What substances neutralize foreign bodies and their poisons in the human and animal body?

1) enzymes

2) antibodies

3) antibiotics

4) hormones

Passive artificial immunity occurs in a person if they are injected into his blood

1) weakened pathogens

2) ready-made antibodies

3) phagocytes and lymphocytes

4) substances produced by pathogens

Phagocytosis is called

1) the ability of leukocytes to leave blood vessels

2) destruction of bacteria and viruses by leukocytes

3) conversion of prothrombin to thrombin

4) transfer of oxygen from the lungs to tissues by red blood cells

Human phagocytes are capable

1) capture foreign bodies

2) produce hemoglobin

Metabolism

The human body receives the building material and energy necessary for life in the process

1) growth and development

2) transport of substances

3) metabolism

4) discharge

Oxygen entering the human body during breathing contributes to

1) the formation of organic substances from inorganic

2) oxidation of organic substances with the release of energy

3) the formation of more complex organic substances from less complex ones

4) release of metabolic products from the body

What substances in the human body determine the intensity and direction of chemical processes that form the basis of metabolism

2) enzymes

3) vitamins

I don’t know how to formulate this and the next question. I couldn’t make it into a table, so I just wrote down the features of carbohydrate metabolism for each tissue. I highly recommend discussing with your teacher before starting work if he offers you such an opportunity.

II. NERVOUS TISSUE

· Nervous tissue uses almost exclusively glucose as an energy source. Glycogen stores are negligible, so the brain is directly dependent on blood glucose supplies.

· In addition, cellular respiration is increased in nervous tissue. The brain consumes a lot of oxygen: 20-25% of the total oxygen consumed by the body. In children up to 50%.

· Aerobic processes predominate, in particular aerobic glycolysis: 85% of glucose is oxidized aerobically (to carbon dioxide and water), 15% anaerobically (to lactate). Anaerobic oxidation is an emergency mechanism.

· The conversion of glucose to glucose-6-phosphate (the main mechanism of glucose involvement in glycolysis) is catalyzed by hexokinase, which has a high affinity for glucose. In this case, the nervous tissue is INSULIN-INDEPENDENT (insulin does not penetrate the blood-brain barrier):
it requires the supply of glucose, even if there is little glucose in the blood and no insulin.

· Under physiological conditions, the role of the pentose phosphate pathway of glucose oxidation in brain tissue is small, but this pathway of glucose oxidation is inherent in all brain cells. The reduced form of NADP (NADPH) formed during the pentose phosphate cycle is used for the synthesis of fatty acids, steroids, neurotransmitters, etc.

III. Reaction:

I'm not sure exactly, but I think this reaction is meant:

8. Describe the differences between carbohydrate metabolism in the liver and carbohydrate metabolism in the erythrocyte. Write the reaction for the formation of 2,3-diphosphoglycerate, what is the role of this metabolite.

In general, it seems to me that this particular task can be presented purely in the form of two diagrams (which are available in the text below), with explanations.

I. LIVER

· The main role of the liver in carbohydrate metabolism: maintaining a constant level of glucose in the blood. The following processes occur in the liver: synthesis and breakdown of glycogen, gluconeogenesis, glycolysis, PPP. All these processes are carried out through glucose-6-phosphate:

· It is worth noting that a special type of hexokinase, glucokinase, is involved in the conversion of glucose into glucose-6 phosphate (it has a low affinity for glucose, is not inhibited by G-6-P,

· In the liver, glycogen exchange occurs very intensively: when there is an excess of glucose in the blood, it is stored in the form of glycogen, and when there is a deficiency, it is mobilized (disintegration of glycogen) from it.

· Glucose biosynthesis occurs in the liver (from AA, fats, lactate). Other dietary monosaccharides (fructose, galactose) can also be converted into glucose.

· PFP reactions occur most intensively in the liver. It is the main source of NADPH for the synthesis of fatty acids, cholesterol, steroid hormones, microsomal oxidation in the liver; It is also the main source of pentoses for the synthesis of nucleotides, nucleic acids, and coenzymes.

II. Erythrocyte

· Red blood cells lack mitochondria, so they can only use glucose (!) as energy material

· About 90% of the incoming glucose is used in anaerobic glycolysis, and the remaining 10% is used in the pentose phosphate pathway.

· The end product of anaerobic glycolysis, lactate, enters the blood plasma and is used in other cells, primarily hepatocytes. ATP, formed in anaerobic glycolysis, ensures the functioning of Na +, K + -ATPase and the maintenance of glycolysis itself.

· Important Feature anaerobic glycolysis in erythrocytes compared to other cells - the presence of the enzyme bisphosphoglycerate mutase in them. Bisphosphoglycerate mutase catalyzes the formation of 2,3-bisphosphoglycerate from 1,3-bisphosphoglycerate.

· Glucose in erythrocytes is also used in the pentose phosphate pathway, the oxidative stage of which ensures the formation of the coenzyme NADP + H +, necessary for the reduction of glutathione.

III. Reaction:

Produced only in erythrocytes, 2,3-bisphosphoglycerate serves as an important allosteric regulator of oxygen binding by hemoglobin.

9. Present in the form of a diagram the processes of converting glucose into triacylglycerols (taking into account the compartmentalization of the process). Describe the physiological role of this process.

Did I mention that I hate diagrams?
So, once again, I don’t know what they want to see. Here I left the enzymes and participants... I didn’t describe glycolysis... but if I attach anything after the main diagram (I repeat, it’s unlikely that it will be needed, but it’s better to let it be).

Compartmentalization:cytoplasm cells.

+ glycolysis to DOAP

II. Physiological role:

In those cases when carbohydrates are consumed in quantities exceeding the body's energy needs , excess calories are stored as triacylglycerols in adipose tissue.

The accumulated excess fat can be used for energy, for example, during fasting.

10. Present in the form of a diagram the processes of converting glucose into cholesterol (taking into account the compartmentalization of the process). Describe the physiological role of this process.

Enzymes and participants are in question. There are not many of them, as in the previous task, so I left them... but perhaps they are not needed. Well, I won’t describe glycolysis exactly here. Even for reinsurance: D

I. Scheme:

Compartmentalization: enzymes that catalyze cholesterol synthesis reactions are contained in the cytoplasm and endoplasmic reticulum many cells (especially hepatocytes).

II. Physiological role:

When excess glucose enters the body, it can be converted into cholesterol in the liver.

Cholesterol performs many functions: it is part of all cell membranes and affects their properties, and serves as the initial substrate in the synthesis of bile acids and steroid hormones.

LDL cholesterol is associated with the risk of developing atherosclerosis.

11. Characterize (list, present in diagram form) the sources and ways of using cholesterol in the liver. Write the reaction catalyzed by β-hydroxy-β-methyl-glutaryl-CoA reductase, indicate the special role of this enzyme in the metabolism of cholesterol.

I. Scheme:

II. Reaction:

III. Role of the enzyme: hydroxymethylglutaryl-CoA reductase limits the rate of cholesterol biosynthesis, therefore, with an excess of cholesterol in food, this enzyme is inactivated and reaction slows down .

12. Write the reaction for the formation of β-hydroxy-β-methyl-glutaryl-CoA from acetyl-CoA. Indicate the ways of using β-hydroxy-β-methyl-glutaryl-CoA in the liver.

I. Reactions:

II. Ways to use the product in the liver:

1) participation in the future ketone body metabolism;
2) participation in cholesterol synthesis.

13. Write the reaction for the formation of acetoacetate from β-hydroxy-β-methyl-glutaryl-CoA. Write the reactions for the utilization of acetoacetate. Indicate the localization and physiological role of these processes.

I. Reaction of formation of acetoacetate:

Localization:liver (mitochondria);

II. Acetoacetate utilization reactions:

They transport glucose between cells and blood along a concentration gradient (in contrast to transporters that transport MSH when they are absorbed in the intestine against a concentration gradient). GluT1 is located in the endothelium of the BBB. It serves to provide glucose to the brain. GluT2 in the intestinal wall, liver and kidneys - organs that release glucose into the blood. GluT3 is found in neurons in the brain. GluT4 is the main glucose transporter in muscle and adipocytes. GluT5 is found in small intestine, details of its function are unknown.

The following cells and tissues use glucose especially intensively: 1) nervous tissue, because for her, glucose is the only source of energy, 2) muscles (to produce energy for contractions), 3) intestinal wall (absorption processes of various substances require energy), 4) kidneys (urine formation is an energy-dependent process), 5) adrenal glands (energy is required for the synthesis of hormones); 6) red blood cells; 7) adipose tissue (glucose is necessary for it as a source of glycerol for the formation of TAG); 8) mammary gland, especially during lactation (glucose is necessary for the formation of lactose).

In tissues, about 65% of glucose is oxidized, 30% goes to liponeogenesis, 5% to glycogenogenesis.

The glucostatic function of the liver is ensured by three processes: 1) glycogenogenesis, 2) glycogenolysis, 3) gluconeogenesis (synthesis of glucose from intermediate products of the breakdown of proteins, lipids, carbohydrates).

When blood glucose increases, its excess is used for the formation of glycogen (glycogenogenesis). When the blood glucose level decreases, glycogenolysis (glycogen breakdown) and gluconeogenesis increase. Under the influence of alcohol, gluconeogenesis is inhibited, which is accompanied by a drop in blood glucose when large quantities drunk alcohol. Liver cells, unlike other cells, are capable of passing glucose in both directions depending on the glucose concentration in intercellular substance and blood. Thus, the liver performs a glucostatic function, maintaining a constant blood glucose level, which is 3.4-6.1 mmol/l. Physiological hypoglycemia is observed until days after birth, this is due to the fact that the connection with the mother after childbirth ceased, and there are few glycogen reserves.

Glycogenogenesis 5% of glucose is converted to glycogen. The formation of glycogen is called glycogenogenesis. 2/5 of glycogen reserves (approximately 150 grams) are deposited in the liver parenchyma in the form of clumps (10% of the wet weight of the liver). The rest of the glycogen is stored in muscles and other organs. Glycogen serves as a reserve of blood glucose for all organs and tissues. The reserve of GW in the form of glycogen is due to the fact that glycogen, as an IUD, unlike glucose, does not increase osmotic pressure cells.

Glycogenogenesis is a complex, multi-stage process that consists of the following stages - reactions know (text only) see. materials page 35:

1 - Formation of glucose-6-phosphate - in the liver under the action of glucokinase, and in other tissues under the action of hexokinase, glucose is phosphorylated and converted into glucose-6-phosphate (irreversible reaction).

2 - Conversion of glucose-6-phosphate into glucose-1-phosphate Under the action of phosphoglucomutase, glucose-1-phosphate is formed from glucose-6-phosphate (reversible reaction).

3 - Formation of UDP-glucose - glucose-1-phosphate interacts with UTP under the action of UDPG pyrophosphorylase and UDP-glucose and pyrophosphate are formed (reversible reaction)

4 - Elongation of the glycogen chain begins with the activation of the glycogenin enzyme: UDP-glucose interacts with the OH group of tyrosine in the glycogenin enzyme (UDP is cleaved off and subsequently, upon rephosphorylation, again produces UTP). Then glycosylated glycogenin interacts with glycogen synthase, under the influence of which up to 8 more UDP-glucose molecules are added to the first glucose residue through 1-4 bonds. In this case, UDP is split off (for reactions, see page Biochemistry in diagrams and figures, 2nd ed. - N.R. Ablaev).

5 - Branching of the glycogen molecule - under the action of amylo(14)(16)-transglucosidase, an alpha(16)-glycosidic bond is formed (see film, do not write off).

Thus, 1) glycogen synthetase and amylotransglucosidase take part in the formation of a mature glycogen molecule; 2) glycogen synthesis requires a lot of energy - 1 ATP molecule and 1 UTP molecule are used to attach 1 glucose molecule to a glycogen fragment; 3) to initiate the process, the presence of a glycogen seed and some specialized primer proteins is required; 4) this process is not unlimited - excess glucose is converted into lipids.

Glycogenolysis The process of glycogen breakdown occurs in 2 ways: 1 way - phosphorolysis, 2 way - hydrolysis.

Phosphorolysis occurs in many tissues (we write the reactions immediately, open text only). In this case, phosphoric acids are added to the outer glucose molecules and at the same time they are eliminated in the form of glucose-1-phosphates. Phosphorylase accelerates the reaction. Glucose-1-phosphate then turns into glucose-6-phosphate, which does not penetrate the cell membrane and is used only where it is formed. This process is possible in all tissues except the liver, which contains a lot of the enzyme glucose-6-phosphatase, which accelerates the cleavage of phosphoric acid and thus forms free glucose, which can enter the blood - show on film, know the reactions, see materials p. 36 -37 (do not write off on open).

Must be in text form - Phosphorylase does not act on alpha(16)glycosidic bonds. Therefore, the final destruction of glycogen is carried out by amylo-1,6-glucosidase. This enzyme exhibits 2 types of activity. First, transferase activity, which transfers a fragment of 3 glucose molecules from the alpha (16) position to the alpha (14) position. Secondly, glucosidase activity, which accelerates the cleavage of free glucose at the level of the alpha(16) glycosidic bond (see film).

The second pathway of glycogenolysis, hydrolysis, occurs primarily in the liver under the action of gamma amylase. In this case, the last molecule of glucose is split off from glycogen and free glucose can enter the blood of the reaction, see materials on page 37, show on film.

Thus, as a result of glycogenolysis, either glucose-monophosphate (during phosphorolysis) or free glucose (during hydrolysis) is formed, which is used for synthetic processes or undergoes breakdown (oxidation).

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Conversion of glucose in cells

When glucose enters cells, glucose phosphorylation occurs. Phosphorylated glucose cannot pass through the cytoplasmic membrane and remains in the cell. The reaction requires ATP energy and is practically irreversible.

General scheme of glucose transformation in cells:

Glycogen metabolism

The pathways for the synthesis and breakdown of glycogen are different, which allows these metabolic processes to occur independently of each other and eliminates the switching of intermediate products from one process to another.

The processes of synthesis and breakdown of glycogen are most active in the cells of the liver and skeletal muscles.

Glycogen synthesis (glycogenesis)

Glycogen synthase, the key enzyme of the process, catalyzes the addition of glucose to the glycogen molecule to form a-1,4-glycosidic bonds.

Glycogen synthesis scheme:

The inclusion of one glucose molecule into the synthesized glycogen molecule requires the energy expenditure of two ATP molecules.

Regulation of synthesis glycogen is carried out through the regulation of glycogen synthase activity. Glycogen synthase is present in cells in two forms: glycogen synthase in (D) - phosphorylated inactive form, glycogen synthase a (I)- non-phosphorylated active form. Glucagon in hepatocytes and cardiomyocytes inactivates glycogen synthase through the adenylate cyclase mechanism. Adrenaline acts similarly in skeletal muscles. Glycogen synthase D can be allosterically activated by high concentrations of glucose-6-phosphate. Insulin activates glycogen synthase.

So, insulin and glucose stimulate glycogenesis, adrenaline and glucagon inhibit it.

Glycogen synthesis by oral bacteria. Some oral bacteria are able to synthesize glycogen when there is an excess of carbohydrates. The mechanism of glycogen synthesis and breakdown by bacteria is similar to that of animals, except that ADP derivatives, rather than UDP derivatives of glucose, are used for synthesis. Glycogen is used by these bacteria to support life in the absence of carbohydrates.

Glycogen breakdown (glycogenolysis)

The breakdown of glycogen in muscles occurs during muscle contractions, and in the liver - during fasting and in between meals. The main mechanism of glycogenolysis is phosphorolysis (cleavage of a-1,4-glycosidic bonds with the participation of phosphoric acid and glycogen phosphorylase).

Scheme of glycogen phosphorolysis:

Differences in glycogenolysis in liver and muscle. Hepatocytes contain the enzyme glucose-6-phosphatase and free glucose is formed, which enters the blood. Myocytes do not contain glucose-6-phosphatase. The resulting glucose-6-phosphate cannot leave the cell into the blood (phosphorylated glucose does not pass the cytoplasmic membrane) and is used for the needs of myocytes.

Regulation of glycogenolysis. Glucagon and adrenaline stimulate glycogenolysis, insulin inhibits it. Regulation of glycogenolysis is carried out at the level of glycogen phosphorylase. Glucagon and adrenaline activate (convert to phosphorylated form) glycogen phosphorylase. Glucagon (in hepatocytes and cardiomyocytes) and adrenaline (in myocytes) activate glycogen phosphorylase via a cascade mechanism through an intermediary - cAMP. By binding to their receptors on the cytoplasmic membrane of cells, hormones activate the membrane enzyme adenylate cyclase. Adenylate cyclase produces cAMP, which activates protein kinase A, and a cascade of enzyme transformations is launched, ending with the activation of glycogen phosphorylase. Insulin inactivates, that is, converts glycogen phosphorylase into a non-phosphorylated form. Muscle glycogen phosphorylase is activated by AMP through an allosteric mechanism.

Thus, glycogenesis and glycogenolysis are coordinately regulated by glucagon, adrenaline and insulin.

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Conversion - glycogen

The conversion of glycogen into glucose is carried out in the liver by phosphorolysis with the participation of the enzyme L-glucan phosphorylase. During phosphorolysis, glycogen breaks down to form glucose-1-phosphate (Cori ester) without prior conversion to dextrins and maltose. Glucose-1 - phosphate is dephosphorylated under the influence of phosphatase (glucose-1 - phosphatase), and free glucose enters the blood. In the liver, in addition to the phosphorolytic breakdown of glycogen, there is also a hydrolytic breakdown pathway with the participation of the enzyme amylase.

Glycogen phosphorylase catalyzes the conversion of stored glycogen to glucose-1-phosphate. Glucose-1-phosphate serves as a precursor to glucose-6-phosphate, an intermediate product of glycolysis. During intense work, skeletal muscles require large amounts of glucose-6-phosphate. At the same time, in the liver, glycogen consumption is used to maintain a constant level of glucose in the blood in the intervals between meals, b) In actively working muscles, where the need for ATP is very high, it is necessary for glucose-1 - phosphate to be formed quickly - this requires a large Ktah.

The problem proposes to study the conversion of glycogen by muscle extracts that do not contain mitochondria, in the presence of iodoacetate and without it.

Oxidative phosphorylation, which occurs during the conversion of glycogen to lactic acid, involves the transformation of oxidative energy into energy-rich ester bonds. These bonds arise when the alcohol group of an aldehyde or keto alcohol interacts with phosphoric acid.

The first reaction of the glycolytic cycle in muscles is the conversion of glycogen into glucose 1-phosphate (Cori ester) under the action of muscle phosphorylase and with the help of inorganic phosphate.

The above diagram is arbitrary, and it does not reflect those abnormal transformations of glycogen that were mentioned at the beginning of our message.

The remaining processes during meat ripening are associated with glycosis - the conversion of glycogen into lactic acid, denation and proteolysis, the partial breakdown of mainly sarco-metabolic proteins into peptides and amino acids. These processes occur at 0 C and intensify with increasing temperature, leading to softening of the tissue and improvement of the organoleptic properties of the meat.

Hyperglycemia (and associated glycosuria) can be caused by the action of the adrenal hormone, adrenaline, which stimulates the conversion of glycogen into glucose.

He noted that metabolic reactions that enhance ATP synthesis receive positive feedback from ADP; these reactions are included in the processes of converting glycogen into glucose, as well as glucose into pyruvic acid through the glycolytic pathway; they are also involved in the process of providing electrons for oxidative phosphorization in mitochondria through the conversion of pyruvic acid into carbon dioxide in the citric acid formation cycle. The rates of glycolysis and the reaction of introducing pyruvic acid into the citric acid formation cycle, on the contrary, receive negative feedback from ATP. The combined effect of feedback is to accelerate glycolysis and oxidative phosphorization to enhance ATP synthesis when ATP use increases and to slow down the same reactions when ATP use decreases.

He noted that metabolic reactions that enhance ATP synthesis receive positive feedback from ADP; these reactions are included in the processes of converting glycogen into glycogen, as well as glucose into pyruvic acid through the glycolytic pathway; they are also involved in the process of providing electrons for oxidative phosphorusation in mitochondria through the conversion of pyruvic acid into carbon dioxide in the citric acid formation cycle. The rates of glycolysis and the reaction of introducing pyruvic acid into the citric acid formation cycle, on the contrary, receive negative feedback from ATP. The combined effect of feedback is to accelerate glycolysis and oxidative phosphorization to increase ATP synthesis when ATP use increases, and to slow down the same reactions when ATP use decreases.

A detailed study of cosimase was preceded by the discovery by O. Meyerhof of the fact that muscle juice, in order to convert glycogen into lactic acid, needs a coenzyme similar in its properties to coenzyme 1 discovered by A.

Glucagon has a dual effect: it accelerates the breakdown of glycogen (glycolysis, glycogenolysis) and inhibits its synthesis from. UDP-glucose, the overall result of which is the acceleration of the conversion of liver glycogen into glucose. The hyperglycemic effect of glucagon is also provided by gluconeogenesis, which is longer in duration than glycolysis.

Thus, adrenaline has a double effect on carbohydrate metabolism: it inhibits the synthesis of glycogen from UDP-glucose, since very high concentrations of glucose-6-phosphate are required for the maximum activity of the D-form of glycogen synthase, and it accelerates the breakdown of glycogen, since it promotes the formation of active phosphorylase a . In general, the net effect of adrenaline is to accelerate the conversion of glycogen into glucose.

Metabolites are intermediate products formed during stepwise metabolic reactions. They are usually found in tissues in low concentrations. For example, lactic acid is one of the metabolites formed during the conversion of glycogen to carbon dioxide and water.

To convert the inactive form into an active one, the presence of a special enzyme is necessary, as well as Mg2 and adenosine-3 5-phosphate (cyclic adenylate; see chapter. The formation of adenosine-3 5-phosphate from ATP is catalyzed by a specific enzyme adenyl cyclase, the activity of which is stimulated by adrenaline, a hormone which is a catecholamine. It is known that adrenaline is a powerful stimulator of glycogen catabolism in vivo; it causes the conversion of glycogen into glucose, which enters the blood; excess glucose into the blood leads to hyperglycemia.

Conversion of glucose into glycogen

Most muscles in the body use mainly carbohydrates for energy; for this, they are broken down through glycolysis to pyruvic acid, followed by its oxidation. However, the process of glycolysis is not the only way in which glucose can be broken down and used for energy purposes. Another important mechanism for the breakdown and oxidation of glucose is the pentose phosphate pathway (or phosphogluconate pathway), which is responsible for 30% of glucose breakdown in the liver, which exceeds its breakdown in fat cells.

This pathway is especially important because it provides cells with energy independently of all the enzymes of the citric acid cycle, therefore it is an alternative pathway for energy exchange in cases of disturbances in the enzyme systems of the Krebs cycle, which is fundamentally important for providing energy to numerous synthesis processes in cells.

The release of carbon dioxide and hydrogen in the pentose phosphate cycle. The figure shows most of the basic chemical reactions of the pentose phosphate cycle. It can be seen that at various stages of glucose conversion, 3 molecules of carbon dioxide and 4 hydrogen atoms can be released to form a sugar containing 5 carbon atoms - D-ribulose. This substance can be successively converted into various other five-, four-, seven- and three-carbon sugars. As a result, glucose can be resynthesized through various combinations of these carbohydrates.

In this case, only 5 glucose molecules are resynthesized for every 6 molecules that initially entered into the reaction, so the pentose phosphate pathway is a cyclic process, leading to the metabolic breakdown of one glucose molecule in each completed cycle. When the cycle repeats, all glucose molecules are converted into carbon dioxide and hydrogen. Hydrogen then enters into oxidative phosphorylation reactions, forming ATP, but more often it is used for the synthesis of fats and other substances in the following way.

The use of hydrogen for the synthesis of fats. Functions of nicotinamide adenine dinucleotide phosphate. The hydrogen released during the pentose phosphate cycle does not combine with NAD+, as during glycolysis, but reacts with NADP+, which is almost identical to NAD+, except for the phosphate radical. This difference is significant because Only when bound to NADP+ to form NADP-H can hydrogen be used to form fats from carbohydrates and synthesize some other substances.

When the glycolytic process of glucose utilization slows due to less cellular activity, the pentose phosphate cycle remains active (especially in the liver) and ensures the breakdown of glucose, which continues to enter the cells. The resulting NADP-H in sufficient quantities promotes the synthesis of long chains of fatty acids from acetyl-CoA (a derivative of glucose). This is another way that ensures the use of the energy contained in the glucose molecule, but in this case for the formation not of ATP, but of fat reserves in the body.

Conversion of glucose into glycogen or fats

If glucose is not immediately used for energy needs, but its excess continues to enter the cells, it begins to be stored in the form of glycogen or fat. As long as glucose is stored primarily in the form of glycogen, which is stored in the maximum possible quantity, this amount of glycogen is sufficient to meet the body's energy needs for a period of time.

If glycogen-storing cells (mainly liver and muscle cells) approach the limit of their glycogen storage capacity, the continued supply of glucose is converted into fats in liver and adipose tissue cells, which are sent for storage in adipose tissues.

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What happens in the liver with excess glucose? Scheme of glycogenesis and glycogenolysis

Glucose is the main energy material for the functioning of the human body. It enters the body with food in the form of carbohydrates. Over the course of many millennia, man has undergone a lot of evolutionary changes.

One of the important acquired skills was the body’s ability to store energy materials for future use in case of famine and synthesize them from other compounds.

Excess carbohydrates accumulate in the body with the participation of the liver and complex biochemical reactions. All processes of accumulation, synthesis and use of glucose are regulated by hormones.

What role does the liver play in storing carbohydrates in the body?

There are the following ways for the liver to use glucose:

1. Glycolysis. A complex multi-stage mechanism of glucose oxidation without the participation of oxygen, which results in the formation of universal energy sources: ATP and NADP - compounds that provide energy for all biochemical and metabolic processes in the body;
2. Storage in the form of glycogen with the participation of the hormone insulin. Glycogen is an inactive form of glucose that can accumulate and be stored in the body;
3. Lipogenesis. If more glucose is supplied than is necessary even for the formation of glycogen, lipid synthesis begins.

The role of the liver in carbohydrate metabolism is enormous; thanks to it, the body constantly has a supply of carbohydrates that are vital for the body.

What happens to carbohydrates in the body?

The main role of the liver is the regulation of carbohydrate metabolism and glucose with the subsequent deposition of glycogen in human hepatocytes. A special feature is the transformation of sugar under the influence of highly specialized enzymes and hormones into its special form; this process occurs exclusively in the liver (a necessary condition for its consumption by cells). These transformations are accelerated by the enzymes hexo- and glucokinase when the sugar level decreases.

During the digestion process (and carbohydrates begin to break down immediately after food enters the oral cavity), the glucose content in the blood increases, resulting in an acceleration of reactions aimed at deposition of excess. This prevents the occurrence of hyperglycemia during meals.

Sugar from the blood, through a series of biochemical reactions in the liver, is converted into its inactive compound - glycogen and accumulates in hepatocytes and muscles. When energy starvation occurs, with the help of hormones, the body is able to release glycogen from the depot and synthesize glucose from it - this is the main way to obtain energy.

Glycogen synthesis scheme

Excess glucose in the liver is used in the production of glycogen under the influence of the pancreatic hormone insulin. Glycogen (animal starch) is a polysaccharide, the structural feature of which is a tree-like structure. It is stored by hepatocytes in the form of granules. The glycogen content in the human liver can increase up to 8% of the cell mass after eating a carbohydrate meal. Breakdown is generally needed to maintain glucose levels during digestion. With prolonged fasting, glycogen content drops to almost zero and is synthesized again during digestion.

Biochemistry of glycogenolysis

If the body's need for glucose increases, glycogen begins to break down. The conversion mechanism occurs, as a rule, between meals, and is accelerated during muscle loads. Fasting (no food intake for at least 24 hours) leads to almost complete breakdown of glycogen in the liver. But with regular nutrition, its reserves are completely restored. Such accumulation of sugar can exist for a very long time, before the need for breakdown arises.

Biochemistry of gluconeogenesis (pathway to glucose production)

Gluconeogenesis is the process of synthesis of glucose from non-carbohydrate compounds. Its main task is to maintain a stable level of carbohydrates in the blood during a lack of glycogen or heavy physical work. Gluconeogenesis ensures the production of sugar up to 100 grams per day. In a state of carbohydrate starvation, the body is able to synthesize energy from alternative compounds.

To use the glycogenolysis pathway when necessary to obtain energy, the following substances are needed:

1. Lactate (lactic acid) is synthesized during the breakdown of glucose. After physical activity, it returns to the liver, where it is again converted into carbohydrates. Due to this, lactic acid is constantly involved in the formation of glucose;
2. Glycerol is the result of lipid breakdown;
3. Amino acids are synthesized during the breakdown of muscle proteins and begin to participate in the formation of glucose when glycogen reserves are depleted.

The main amount of glucose is produced in the liver (more than 70 grams per day). The main task of gluconeogenesis is to supply sugar to the brain.

Carbohydrates enter the body not only in the form of glucose - it can also be mannose contained in citrus fruits. Mannose, as a result of a cascade of biochemical processes, is converted into a compound similar to glucose. In this state, it enters into glycolysis reactions.

Scheme of the regulatory pathway for glycogenesis and glycogenolysis

The pathway of glycogen synthesis and breakdown is regulated by the following hormones:

• Insulin is a pancreatic hormone of protein nature. It lowers blood sugar. In general, a feature of the hormone insulin is its effect on glycogen metabolism, as opposed to glucagon. Insulin regulates the further pathway of glucose conversion. Under its influence, carbohydrates are transported into the cells of the body, and from their excess, glycogen is formed;
• Glucagon, the hunger hormone, is produced by the pancreas. It has a protein nature. In contrast to insulin, it accelerates the breakdown of glycogen and helps stabilize blood glucose levels;
• Adrenaline is a hormone of stress and fear. Its production and secretion occur in the adrenal glands. Stimulates the release of excess sugar from the liver into the blood to supply tissues with “nutrition” in a stressful situation. Just like glucagon, unlike insulin, accelerates the catabolism of glycogen in the liver.

A change in the amount of carbohydrates in the blood activates the production of the hormones insulin and glucagon, changing their concentration, which switches the breakdown and formation of glycogen in the liver.

One of the important tasks of the liver is to regulate the lipid synthesis pathway. Lipid metabolism in the liver includes the production of various fats (cholesterol, triacylglycerides, phospholipids, etc.). These lipids enter the blood, their presence provides energy to the body's tissues.

The liver is directly involved in maintaining energy balance in the body. Her diseases can lead to disruption of important biochemical processes, as a result of which all organs and systems will suffer. It is necessary to carefully monitor your health and, if necessary, do not delay visiting a doctor.

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